The present invention relates, in general, to a an electromotive servo drive.
Nothing in the following discussion of the state of the art is to be construed as an admission of prior art.
An electromotive drive typically includes a drive motor and a drive train, which is provided with an output member and includes at least a gear stage for rotation speed reduction, and a rotatable hand-operated adjusting shaft for adjusting the output member of the servo drive and/or the control member coupled therewith. Electromotive servo drives involved here can be used in a wide variety of constructions for adjusting mechanical control members, e.g. for effecting a controlled operation of flaps in the field of heating, venting and air-conditioning. The output rotation speeds of the drive motors of the servo drives are relatively high whereas the speeds of the control members to be driven or the rotation speeds of the output members are relatively small so that there is a need for several gear stages to reduce the rotation speeds. The individual gear stages typically include two toothed gears with an extremely high ratio of tooth numbers. For safety reasons, the servo drives are provided with a pull-back spring element which moves the control member, connected to the servo drive, to a certain position, during a power outage, for example. The drive motors are normally associated to brakes which are so configured as to effect a blocking of the drive train, when the motor has stopped, but are moved to a clearing position, when the motor starts to run. The drives must be equipped with a hand-operated adjusting shaft in order to be able to move the output member and/or the control member coupled therewith into at least a predetermined end position which preferably should be targeted when the drive motor is turned on. For that purpose, servo drives known heretofore are provided with a crank.
It would be desirable and advantageous to provide an improved electromotive servo drive to obviate prior art shortcomings and to prevent a return movement of at least one portion of the drive train that is associated to the output member.